Pump drives connected to a container or the like are used for many purposes, such as pumping groundwater or service water from a well or pumping other liquid from a container. When the material being pumped is limited, it is possible that the pump cannot be used at constant power all the time. A lengthy use of a pump without a flow through the pump can cause overheating in the pump and the material being pumped, and consequently damage the pump drive.
In known arrangements, pumps can be controlled utilizing surface measuring techniques, such as measuring sensors based on ultra-sound or pressure. Measuring sensors of this type can provide accurate surface data. The flow of the pump can be adjusted to provide the desired surface level. Pump control may also be done by using a cable float level switch or mounted float level switch. With these, pumping between the top and bottom limits of the surface can often be implemented with on/off control without adjustment.
There is always a risk that measuring sensors break, so they reduce the reliability of the operation of the apparatus. For instance, a float level switch can, in time, break due to humidity. Also, contact terminal connection problems may occur. In addition, measuring sensors, their cabling, and the extra work needed to install and service them can cause additional costs.